The present invention relates, in general, to semiconductors, and more particularly, to semiconductor processing methods.
In the past, the semiconductor industry had used photolithography lift-off techniques to form conductor patterns on semiconductor wafers. These previous lift-off techniques used solvents such as chlorobenzene to alter the reaction between a photoresist and a photoresist developer solution in order to form an undercut or retrograde profile on the sidewalls of the photoresist. Chlorobenzene, the typical solvent used to modify the reaction between the developer solution and the photoresist, was considered to be a hazardous material. Consequently, use of such hazardous materials required special handling precautions during manufacturing and required special disposal methods.
In addition, the previous lift-off techniques, which used solvents such as chlorobenzene, often did not produce a smooth retrograde profile. That is, portions of the photoresist's sidewall had rough sections or ridges. These rough areas provided a bridge that allowed the conductor material that was to be lifted-off the semiconductor wafer to be attached to the conductor material that was to remain on the wafer. Consequently, lifting-off the unwanted conductor material often resulted in disturbing the desired conductor material that was to be left on the wafer.
Accordingly, it is desirable to have a metal lift-off technique that does not use hazardous materials such as chlorobenzene, that forms a smooth retrograde profile in the photoresist, and that facilitates removing undesirable conductor material without disturbing the desired conductor material.